1. Field of the Invention
This invention relates to a surface fastener molded integrally of synthetic resin comprising a pair of upper and lower engaging members in which a plurality of rows of hook elements are integrally molded of synthetic resin on surfaces of respective engaging base plates and which adopt the same structures to facilitate the manufacture and the control of products and to assure uniform distribution of engaging strength and durability.
2. Description of Prior Art
The usual surface fastener is known as a so-called velvet type fastener comprising a pair of male and female tapes, wherein an engaging element of male tape is formed as hook-like pojection by cutting a part of a loop in the fastener made of knitted cloth, or an engaging element of male tape is formed as a hook-like, mushroom-like, anchor-like projection in the fastener molded integrally of synthetic resin, and an engaging element of female tape is mainly formed of a loop of a loop knitted cloth.
As stated above, the other engaging element or female element is formed of the loop of the loop knitted cloth to provide high engaging ability; however, the female element has weaker strength and is too flexibile. As a result, the female element has not been used as the industrial material since it does not meet the demand of positioning function and the durability.
The conventional surface fasteners made of synthetic resin are disclosed for examples in U.S. Pat. No. 2,499,898, Japanese Utility Model Unexamined Publication No. S 52-71808, and No. H 2-127205. Each of these surface fasteners comprises a pair of upper and lower (or male and female) engaging members which are respectively molded integrally of synthetic resin, so that these fasteners provide excellent positioning function and high strength of engaging elements in comparison with using female members of loop knitted clothes.
However, the above-mentioned surface fasteners comprise male and female engaging elements of mainly mushroom-shape. When the engaging element has a mushroom shape, the construction of the engaging element provides engaging strength weaker than that of the engaging element of hook-shape. When engaging and disengaging of the male and female elements are repeated, the engaging strength falls off in a short time, so that the fastener will be hardly usable.
A precedent surface fastener comprising a pair of male and female engaging elements of the same hook shape is proposed to solve the above-mentioned problems of the conventional surface fastener (Japanese Utility Application No. H 4-27364). This surface fastener is composed first and second engaging members which are respectively provided with a plurality of rows of hook elements. The hook elements of first and second engaging members are oriented in mutually opposite directions, and the pitch of hook elements on the first engaging member is set at twice as much as the pitch of hook elements of the second engaging member.
In order to engage hook elements of a first engaging member surely with hook elements of a second engaging member, it is required to guide and engage a hook element of the first engaging member between a pair of hook elements of the second engaging member in the row direction. During this guiding, hook elements of the first engaging member should be elastic-deformed separating mutually. In order to allow the elastic deformation in the mutually separating direction, it is considered to increase the pitch between hooks on both the first and second engaging members, however the density of the hook elements becomes rough so that the engaging strength deteriorates inevitably. The above-mentioned prior surface fastener is developed on general investigation of the above-mentioned problems. Since hook elements are engaged with each other to provide remarkably high engaging strength and stable form and to prevent its strength from decreasing in repeated engagement, the surface fastener can be used as suitable industrial materials.
The above-mentioned integrally molded surface fastener of this construction has the above-mentioned excellent qualities. But on the further investigation of this construction, it is found to be unsatisfactory.
That is, this surface fastener is composed of first and second engaging members of different constructions, so that it is required to form respective engaging members independently in manufacturing of the surface fastener. It is moreover required to classify first and second engaging members completely for the stock control of products and to confirm the combination and the number of combined first and second engaging members in ordering and receiving the order of products.
Further, since it is required to confirm that one is the first engaging member and the other is the second engaging member to attach both products, attaching work will be rather complicated.